Lysosomal hydrolases of neutrophils have an important role for an organism defense reaction against tissue damage caused by microbe or inflammation etc.
Elastase and cathepsin G, which belong to neutral serine proteinase locally existed in azurophil granule mainly play a part in decomposition of a connective tissue.
Especially, elastase degrades elastic connective tissue by cleaving the cross-linking of elastin which directly maintains the elasticity of lung tissue etc., and by cleaving hydrophobic part of protein [J. Cell. Biol., 40, 366 (1969)] and degrades the cross-linking area of collagen selectively as well as elastin [J. Biochem., 84, 559 (1978)], and it acts on tissue proteins such as proteoglycans etc. [J. Clin. Invest., 57, 615 (1976)]. Therefore, elastase plays an important role in metabolism of connective tissue.
Elastase is inactivated by .alpha..sub.1 -proteinase inhibitor (.alpha..sub.1 -PI) that is a common inhibitor for serine, proteinase in vivo and the unbalance of enzyme and inhibitor system causes the destruction of the tissue [Schweiz. Med. Wshr., 114, 895 (1984)].
The turnover of elastin in normal tissue is very slow [Endocrinology, 120, 92 (1978)], but the pathological acceleration in degradation of elastin is found under various unsound state such as pulmonary emphysema [Am. Rev. Respir. Dis., 110, 254 (1974)], atherosclerosis [Lab. Invest., 22, 228 (1970)] and rheumatoid arthritis [in Neutral Proteases of Human Polymorphonuclear Leukocytes, Urban and Schwarzenberg, Baltimore - Munich (1978), page 390], suggesting the relationship of elastase and diseases [Infection.Inflammation.Immunity, 13, 13 (1983)].